If a man held a gun to your head and told you to go downstairs, would you have a choice?

Yes, you would have a choice. You could choose to call his bluff by refusing to go downstairs and risk being shot, or you could obey (and still risk being shot). It's a choice, however, that's made under duress; and it's a choice that's coerced (i.e., where a threat of force or pain or deprivation is brought to bear on the choice by some responsible human agency). Duress makes it difficult if not impossible to deliberate in a clear, rational, and considered way. Coercion raises the stakes to such a point that normal and otherwise relevant alternatives become unreasonable. Because the choice is both coerced and made under duress, one's moral culpability for the choice is generally mitigated and generally no legal contracts made through the choice are considered binding. True, people often say under such circumstances that one "has no choice." This is often an imprecise way of saying something like: "one could not reasonably have chosen otherwise," or "one could not have made an...

Does knowledge require the impossibility of doubt?

In a word, no. In more than a word, it depends, of course, upon how one defines "knowledge." Knowledge is determined or produced through specific sets of procedures and practices such as logical inference, corroborated observation, inspection, controlled experiment, etc.; and even the best of these procedures, at least in their application, admit the possibility of doubt. Now, it's true that some philosophers (e.g. Descartes) have cast knowledge as requiring absollute certainty or the complete absence or elimination of doubt. (I'm assuming here that by impossibility of doubt you mean the absenceor elimination of doubt.) But, as far as I can see, it makes more sense and people are better off acknowledging human finnitude and abandoning this requirement. Interestingly, you didn't ask whether "truth" or "certainty" require the impossibility of doubt. Consider how those questions might lead to different answers.

Can the proposition, "God is unknowable" be defended? If something is unknowable, how can we know that it is unknowable?

You raise an interesting issue. At the outset, I'm afraid, I must say that much depends upon what in this sentence is meant by "knowable." On the face of it, however, the statement "X is unknowable" is paradoxical, even incoherent. To use the name or term, "X." meaningfully seems possible only if something is known about X. Still, it seems to make sense to say things like, "The velocity and position of an electron are unknowable" (by the Heisenberg uncertainty principle); "The temperature of every meter foot of atmosphere on the planet currently closest to Alpha Centauri is unknowable"; "The Power Ball number for the next lottery is unknowable today." "The last thought of Abraham Lincoln is unknowable." "The name of every human being is unknowable." Of course, none of these statements imply that nothing at all is known about the topics they address. We can know, for example, that the last thought that crossed through Abraham Lincoln's mind was a thought, that the Power Ball number will be...

if every one is just a product of their environment, then how are there original ideas, art, and imagination?

Why can't environment produce original events? Let's say that every human being possesses a unique (original?) DNA sequence. One might say that a DNA sequence is a product of environment. Why not consider "original" ideas in the same manner--that is, as new combinations of precedent ideas? Would new species count as "original"? What do you mean by original? Perhaps you mean an utterly new, different, and original idea, art, or imagination. I have my doubts that such things are possible. I also have my doubts that ideas, art, and imaginations are "products" or environment. What do you mean by "product"? It seems to carry a rather industrial or commercial connotation. Might it be a tendentious term?

Is telepathy possible? I have never had a telepathic experience and nor have I met anyone who claims to have had one. I think I would be pretty sceptical if I did. But is it even possible to have a telepathic experience? How would you know you weren't the victim of some kind of psychosis? How would you be able to sort out the 'ownership' of thoughts and other mental states? When I think about telepathy I imagine it as some kind of telephony without the instruments and wires. Let's say I wanted to communicate with my friend Sandra. With a telephone I pick up the instrument, dial Sandra's number, hear some rings and clicks and then I hear Sandra saying 'Hello' (or whatever). I know it's Sandra because I recognise her voice. I know it wasn't me saying 'Hello' because I didn't open my mouth. But with telepathy all the physical actions and events seem to be eliminated. If I want to communicate with Sandra I presumably 'tune in' to her brain somehow. But then all sorts of problems start. How do I know I...

I doubt telepathy is possible, as I can't figure out any causal mechanism to make it work. But that's an empirical matter. I'm reluctant to rule it out in any a priori sense. Must one "know" that the content of a telepathic event is some specified other's thought or mental state? Suppose I'm reading an e-mail or engaged in Instant Messaging with someone. Clearly, I am in some sense apprehending their thoughts (or at leat their words). I do so, however, even if I don't know who the other person is, even if I'm mistaken about who it is, etc. Perhaps, someone has hacked into my friend's IM account or is impersonating my friend in an e-mail. So what? The words I apprehend remain meaningful. In the case of telepathy, one worry (as you point out), however, is that the supposed telepath might simply be apprehending her own thoughts and attributing them to others. But couldn't it go the other way, too? Couldn't one apprehend another's thought and mistakenly take it for one's own? If so, then one could...

Socrates said, "All I know is that I know nothing". What I'm trying to figure out is this: if I know NOTHING, how do I KNOW that I know nothing? It just goes round in circles thus becoming nothing more than a paradox. Would you agree?

This dimension of Socrates' thought has been, of course, highly influential with skeptics. Indeed, it was in part on the basis of this sort of gesture in Plato's works that the Academic skeptics regarded themselves as inheritors of Platonic philosophy. Later the idea became known as "learned ignorance," for example in Nicholas of Cusa's work by the same name. It's an interesting thing to examine the different ways philosophers have tried to cope with the constellation of ideas involved with coming to understand one's ignorance, as well as other dimensions of human finitude. Hellenistic and Greco-Roman skeptics explored the ways in which doubt my characterize humanity's relationship to knowlegdge and whether skeptical arguments advance any positive wisdom or simply tear things down. Montaigne formulated the now-classic, "What do I know?" Erasmus called himself a "foolospher." Hume explored concepts of "natural," "common," ordinary, and non-dogmatic forms of belief while still acknowledging skeptical...

Which of these is a better life? Live fast; die young - a life filled with excitement passion and adventure which ends abruptly on your 30th birthday. Or: Slow and steady wins the race - a life of contentment and satisfaction but little out of the ordinary which lasts well into your dotage.

There is no single answer to this question, just as there is no best life. There are many good lives, and many fitting each of these descriptions. Different characters will find different lives good. For myself, I say, on balance the latter is to be preferred. I find myself in agreement with the ancient Epicureans that most agitating passions produce more unhappiness than happiness, and that easy natural pleasures are better than artificial dynamic pleasures. Tranquility punctuated by ecstatic moments looks pretty good from where I sit.

Are there actions which are morally permissable when undertaken by a group but which would be immoral if performed by an individual?

An important philosophical consideration here before you get going on this issue is deciding what you mean by a group. In particular, you might consider whether you buy into what's been called methodological holism which means here, basically, that the whole is more than the sum of its parts. So, an economic class, a nation, a people, a family is more than just the individuals that compose it. Methodological individualism holds just the opposite, namely that the whole is nothing more than the sum of the parts. Would you say that the state is a group? Then, certainly, there are things that this group can do that would be immoral if performed by an individual. For example: imprison people, judge and punish criminals, conduct wars, appropriate property and tax, marry, etc.

Is extreme (very violent) consensual sadomasochism morally wrong? If so, should it be against the law to cause injury by this practice? Or would it be a 'private' matter?

The old principle of liberty that one can do what one likes so long as it doesn't harm others (famously formulated by John Stuart Mill) is challeneged by this sort of issue. What if someone consents to being harmed or even asks to be harmed? Can one consent to be another's slave? My view is that liberty has been found to be such a good thing that it should be maximized. But it does have limits. Sometimes those limits have to do with advancing collective, social, or political goods, like education and equality. Sometimes they involve protecting people from themselves. Why should people be protected from themselves? Because our actions towards ourselves as well as towards others are not matters of simple will disconnected from the structures of character, coercive power relationships, psychological manipulation and pathology, deceit, and plain old stupidity. On this score, I vote for maximal sexual liberty. And so I support undermining compulsory heterosexuality, compulsory binary relationships,...

According to Descartes' demon hypothesis, would it be possible for the demon to deceive us about the rules of logical inference e.g. could my belief in the law of non-contradiction be caused by the demon?

May I weigh in a bit? I think that panelists are right to suggest that while the dream argument addresses the veracity of perception about the world, the demon argument goes farther and addresses mathematical and logical inferences. I'd like, however, to return to Peter Lipton's question about why the cogito survives the demon argument. There's a bit more to say on that score that explains Descartes's position. There's a difference between mathematical and logical inferences and the cogito, and that is that what Descartes finds persuasive about the cogito is not a matter of inference but rather direct intuition. The demon argument works but pointing out that in any discursive movement of thought, from one idea to another, the demon might interfere. Discursive thought, therefore, is dubious. N.B. that's why the example Alexander George quotes is about discursive movements like "adding" and "counting." In this way, Descartes anticipates, in a way, the point Quine makes in his article, "Two...

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